NDJAMENA, CHAD, DEC. 8 -- A U.S. Air Force plane flew about 400 Libyan guerrilla rebels from Chad today as the U.S. Embassy here continued to refuse comment on reports that the United States had been training the men for secret attacks inside Libya.

The C-141 Starlifter touched down briefly at the airport here and quickly loaded the men before taking off. The flight was the second of what U.S. Ambassador Richard Bogosian called an international humanitarian effort.

Diplomats said the men had been flown to Nigeria, but Bogosian said their final destination had not been determined. A Nigerian Foreign Ministry official in Lagos said he had no knowledge of the flights.

Chad's new president, Idriss Deby, told a news conference that, after ousting president Hissene Habre a week ago, his forces had found the men, whom he described as "opponents of the Libyan regime," inside a training camp. "I do not know which country was training them," Deby said.

But diplomats said U.S. military instructors had in recent years been training between 500 and 700 Libyans -- who were among thousands of prisoners captured by Chad in battles between 1983 and 1987 -- as part of an effort to destabilize Gadhafi's government. There have been reports of commando attacks by opponents of Gadhafi in southern Libya, which borders Chad.

More than 400 Libyan prisoners who were said to have remained loyal to Gadhafi's government following their capture were flown to Tripoli last weekend, immediately after Deby took power. Deby, who for years led Habre's military forces against Libya, broke with Habre last year and assembled a rebel force in neighboring Sudan that invaded Chad Nov. 10.

Libya's foreign ministry condemned the U.S. evacuation as "piracy," saying the men had been seized "against their will." But Deby denied that there had been coercion. He said his government had given the men the choice "either to lay down their arms and request refugee status -- and they would have been welcome -- or to leave.

"Chad's national interest is to have no opponents, from whichever country, on its soil," he said.

He said numerous Libyan aircraft landing in Ndjamena in the past week were carrying humanitarian aid. "Libya is giving aid to the Chadian people and we believe this aid is disinterested," Deby said.